1) What patch level is your test farm at? It needs to be at the
same build or later than the farm the databases are from. For a new
farm, I'd put it at February or April 2010's CU.
2) Do other copies of those databases exist in that farm already?
You can only have one copy of a database attached at the same time.
3) Did you detach the database that was created when the web app
was created BEFORE you attached your test databases? Potentially there
can be site collection name collisions (especially for "/" ) and that
can upset SharePoint.
4) Have you checked in the ULS logs for any clues about what the
problem could be?